On the Performance of QPSK Modulation Over Downlink NOMA: From Error Probability Derivation to SDR-Based Validation

In this paper, we study the performance of QPSK modulation in the context of multi-user downlink NOMA with a successive interference canceller (SIC) at the receiver side. The first objective is to evaluate the benefit of such a technique in terms of error probability, regardless of the number of involved users. Analytical derivations on its closed-form have been verified by both simulation and experimental validation. The article uses numerical simulations not only to corroborate the tightness of our theoretical expressions, but also to analyze the problem of power allocation in the two and three users cases. Finally, this paper provides an interplay between NOMA and software radio by building an experimental validation testbed.